317 research outputs found
An Alternative Topological Field Theory of Generalized Complex Geometry
We propose a new topological field theory on generalized complex geometry in
two dimension using AKSZ formulation. Zucchini's model is model in the case
that the generalized complex structuredepends on only a symplectic structure.
Our new model is model in the case that the generalized complex structure
depends on only a complex structure.Comment: 29 pages, typos and references correcte
T-duality and Generalized Kahler Geometry
We use newly discovered N = (2, 2) vector multiplets to clarify T-dualities
for generalized Kahler geometries. Following the usual procedure, we gauge
isometries of nonlinear sigma-models and introduce Lagrange multipliers that
constrain the field-strengths of the gauge fields to vanish. Integrating out
the Lagrange multipliers leads to the original action, whereas integrating out
the vector multiplets gives the dual action. The description is given both in N
= (2, 2) and N = (1, 1) superspace.Comment: 14 pages; published version: some conventions improved, minor
clarification
Detecting Precipitation Climate Changes: An Approach Based on a Stochastic Daily Precipitation Model
2002 Mathematics Subject Classification: 62M10.We consider development of daily precipitation models based
on [3] for some sites in Bulgaria. The precipitation process is modelled as
a two-state first-order nonstationary Markov model. Both the probability
of rainfall occurrance and the rainfall intensity are allowed depend on the
intensity on the preceeding day. To investigate the existence of long-term
trend and of changes in the pattern of seasonal variation we use a synthesis
of the methodology presented in [3] and the idea behind the classical running
windows technique for data smoothing. The resulting time series of model
parameters are used to quantify changes in the precipitation process over
the territory of Bulgaria
Topological twisted sigma model with H-flux revisited
In this paper we revisit the topological twisted sigma model with H-flux. We
explicitly expand and then twist the worldsheet Lagrangian for bi-Hermitian
geometry. we show that the resulting action consists of a BRST exact term and
pullback terms, which only depend on one of the two generalized complex
structures and the B-field. We then discuss the topological feature of the
model.Comment: 16 pages. Appendix adde
Toda Fields on Riemann Surfaces: remarks on the Miura transformation
We point out that the Miura transformation is related to a holomorphic
foliation in a relative flag manifold over a Riemann Surface. Certain
differential operators corresponding to a free field description of
--algebras are thus interpreted as partial connections associated to the
foliation.Comment: AmsLatex 1.1, 10 page
Gauging the Poisson sigma model
We show how to carry out the gauging of the Poisson sigma model in an AKSZ
inspired formulation by coupling it to the a generalization of the Weil model
worked out in ref. arXiv:0706.1289 [hep-th]. We call the resulting gauged field
theory, Poisson--Weil sigma model. We study the BV cohomology of the model and
show its relation to Hamiltonian basic and equivariant Poisson cohomology. As
an application, we carry out the gauge fixing of the pure Weil model and of the
Poisson--Weil model. In the first case, we obtain the 2--dimensional version of
Donaldson--Witten topological gauge theory, describing the moduli space of flat
connections on a closed surface. In the second case, we recover the gauged A
topological sigma model worked out by Baptista describing the moduli space of
solutions of the so--called vortex equations.Comment: 49 pages, no figures. Typos corrected. Presentation improve
The biHermitian topological sigma model
BiHermitian geometry, discovered long ago by Gates, Hull and Roceck, is the
most general sigma model target space geometry allowing for (2,2) world sheet
supersymmetry. By using the twisting procedure proposed by Kapustin and Li, we
work out the type A and B topological sigma models for a general biHermtian
target space, we write down the explicit expression of the sigma model's action
and BRST transformations and present a computation of the topological gauge
fermion and the topological action.Comment: 40 pages, Latex. Analysis of sect. 6 improved; references adde
The Lie algebroid Poisson sigma model
The Poisson--Weil sigma model, worked out by us recently, stems from gauging
a Hamiltonian Lie group symmetry of the target space of the Poisson sigma
model. Upon gauge fixing of the BV master action, it yields interesting
topological field theories such as the 2--dimensional Donaldson-Witten
topological gauge theory and the gauged A topological sigma model. In this
paper, generalizing the above construction, we construct the Lie algebroid
Poisson sigma model. This is yielded by gauging a Hamiltonian Lie groupoid
symmetry of the Poisson sigma model target space. We use the BV quantization
approach in the AKSZ geometrical version to ensure consistent quantization and
target space covariance. The model has an extremely rich geometry and an
intricate BV cohomology, which are studied in detail.Comment: 52 pages, Late
Poisson sigma model on the sphere
We evaluate the path integral of the Poisson sigma model on sphere and study
the correlators of quantum observables. We argue that for the path integral to
be well-defined the corresponding
Poisson structure should be unimodular. The construction of the finite
dimensional BV theory is presented and we argue that it is responsible for the
leading semiclassical contribution. For a (twisted) generalized Kahler manifold
we discuss the gauge fixed action for the Poisson sigma model. Using the
localization we prove that for the holomorphic Poisson structure the
semiclassical result for the correlators is indeed the full quantum result.Comment: 38 page
Localizing the Latent Structure Canonical Uncertainty: Entropy Profiles for Hidden Markov Models
This report addresses state inference for hidden Markov models. These models
rely on unobserved states, which often have a meaningful interpretation. This
makes it necessary to develop diagnostic tools for quantification of state
uncertainty. The entropy of the state sequence that explains an observed
sequence for a given hidden Markov chain model can be considered as the
canonical measure of state sequence uncertainty. This canonical measure of
state sequence uncertainty is not reflected by the classic multivariate state
profiles computed by the smoothing algorithm, which summarizes the possible
state sequences. Here, we introduce a new type of profiles which have the
following properties: (i) these profiles of conditional entropies are a
decomposition of the canonical measure of state sequence uncertainty along the
sequence and makes it possible to localize this uncertainty, (ii) these
profiles are univariate and thus remain easily interpretable on tree
structures. We show how to extend the smoothing algorithms for hidden Markov
chain and tree models to compute these entropy profiles efficiently.Comment: Submitted to Journal of Machine Learning Research; No RR-7896 (2012
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